/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: LXW
 * Date: 2022-01-16
 * Time: 23:19
 */
class Node {
    public int val;
    public Node prev;
    public Node next;
    public Node(int val) {
        this.val = val;
    }
}
public class DoubleLinkedList {
    Node head;
    Node last;
    //头插法
    public void addFirst(int data) {
        Node node = new Node(data);
        if (head == null) {
            head = node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }
    //尾插法
    public void addLast(int data) {
        Node node = new Node(data);
        if (head == null) {
            head = node;
            last = node;
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data) {
        if (index < 0 || index > size()) {
            System.out.println("index位置不合法");
            return;
        }
        Node cur = head;
        Node node = new Node(data);
        while (index != 0) {
            cur = cur.next;
        }
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }
    //查找是否包含关键字key是否在双链表当中
    public boolean contains(int key) {
        Node cur = head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        Node cur = head;
        while (cur != null) {
            if (cur.val == key) {
                if (cur == head) {  // 如果头节点为key
                    head = head.next;
                    if (head != null) {  // 如果是空表
                        head.prev = null;
                    }else {
                        last = null;
                    }
                }else {                   // 头节点不为key
                    cur.prev.next = cur.next; // 头节点和尾节点都必须进行的第一步
                    if (cur.next == null) {  // 尾节点为key
                        last = last.prev;
                    }else {               // 中间位置是key
                        cur.next.prev = cur.prev;
                    }
                }
                return;      // 删完直接return
            }else {
                cur = cur.next;
            }
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key) {
        Node cur = head;
        while (cur != null) {
            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }else {
                        last = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if (cur.next == null) {
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
            }else {
                cur = cur.next;
            }
        }
    }
    //得到双链表的长度
    public int size() {
        int count = 0;
        Node cur = head;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }
    // 打印双链表
    public void display() {
        Node cur = head;
        while (cur != null) {
            System.out.print(cur.val);
            cur = cur.next;
        }
        System.out.println();
    }
    // 清空双链表
    public void clear() {

        while (head != null) {
            Node cur = head.next;
            head.prev = null;
            head.next = null;
            head = cur;
        }
        last = null;
    }
}
